Backup task causing backing LUN to reach full capacity and failing to consolidate disks

Products

• VMware vCenter Server

Issue/Introduction

• VM logs ("vmware.log") consolidation failures due to lock on file “<vmName>.vmdk”.
  
  

  2026-02-03T21:23:01.087Z In(05) vcpu-0 - ConsolidateItemCombine: Failed to open disk '/vmfs/volumes/<DS_UID>/<vmName>/<vmName>-000003.vmdk' for consolidate: Failed to lock the file (5)

   

  2026-02-03T21:23:01.087Z In(05) vcpu-0 - [msg.disklib.lockinfo.vmfs] Locking conflict for file "/vmfs/volumes/<DS_UID>/<vmName>/<vmName>-flat.vmdk". VMFS on-disk lock owner is host with MAC address ########-########-####-<mac_address_of_ESXhost> and VMFS lock mode 0x2.
  
  

• Review datastore the VM files are located on and see other VM(s) listed that should not be using the datastore.

• Review the configs of the disk and confirm it is not configured to be shared across multiple VMs (e.g., “Disk Mode" currently set as “Dependent”, which is not supported for multi-write).

  • For additional details see Enabling or disabling simultaneous write protection provided by VMFS using the multi-writer flag.

Cause

• While multiple VMs have a disk attached (same vmdk) and not configured properly for multi-write (following supported methods), both VMs could try to write to the disk and multiple ESX hosts try to lock the files.

• During disk consolidation (Snapshot deletion) this will cause the consolidation to fail due to the unexpected lock(s) on the file(s).

Resolution

• Work with your backup team and possibly the backup solution vendor to confirm if the VM disk should be attached to the VM or not.

  • If the disk is not properly configured for multi-write disk sharing, it should be removed from the other VM.

  • If it is due to the 3rd party backup solution VM, follow steps from KB Disk consolidation required on VM warning on VM but task fails.

  • Remove the disk from the VM that should not have the disk attached following steps from KB Removing a disk from a virtual machine using the vSphere Client > Remove Device
    • Note: Do NOT select to remove data as the other VM still needs the disk.
  • Attempt to consolidate disks.

Additional Information

The scenario this KB was created from included TSM as the backup solution, and the VM that the disk was also attached to was the TSM backup server appliance VM.